1. Field of the Invention
The present invention relates to a voice coil structure for speaker, especially to an improved speaker voice coil structure, wherein the improved voice coil structure has at least three coils.
2. Description of the Related Art
As is well known, speaker is an energy transformer, capable of transforming electrical energy to sound energy. The operation of an electrical speaker is to transmit an audio signal of an amplifier to a speaker, and when the audio signal is applied to the speaker, a current will flow through a voice coil of the speaker, and a motive force to a paper cone will be generated by the reaction of the current to a magnetic field to produce sound.
With technology making progress, electrical speaker, after years of evolving, has become matured and common seen—it can be found in applications like PA (Public Address), home box, notebook computer, or mobile phone—and has maintained almost fixed ways of voice coil winding and input signal connection.
Please refer to FIG. 1a and FIG. 1b, which illustrate respectively a side view and a top view of a prior art voice coil structure. As is illustrated in the figures, a prior art voice coil structure 100 includes a bobbin 110 and a voice coil 120. The voice coil 120, wound around the bobbin 110, has a first terminal 121 and a second terminal 122, and can have two turns or four turns according to requirement. However, the prior art voice coil structure 100 has only one set of input terminals, so only one impedance option is provided.
Please refer to FIG. 2a and FIG. 2b, which illustrate respectively a side view and a top view of another prior art voice coil structure having two voice coils. As is illustrated in the figures, a prior art voice coil structure 200 includes a bobbin 210, a first voice coil 220 and a second voice coil 230. The first voice coil 220, wound around the bobbin 210, has a first terminal 221 and a second terminal 222. The second voice coil 230, wound around the first voice coil 220, has a third terminal 231 and a fourth terminal 232. Both of the first voice coil 220 and the second voice coil 230 can have two turns or four turns according to requirement. However, although the prior art voice coil structure 200 have two sets of input terminals, the wire of the coils can slip off the bobbin due to insufficient accommodation space when the total number of turns exceeds four. Besides, as the impedance provided between the first terminal 221 and the second terminal 222, and the impedance provided between the third terminal 231 and the fourth terminal 232 are both fixed values—can not be adjusted according to requirement, the application flexibility of the prior art voice coil structure 200 is then limited.
Therefore, there is a need to design a novel voice coil structure for speaker to overcome the mentioned disadvantages.